Purification of ceramic materials by sodium cyanide



Patented July 12, 1932 UNITED STATES PATENT OFFICE EDGAR A. SLAGLE, OF GRANFORD, NEW JERSEY, ASSIGNOR TO AMERICAN SMELTING AND REFINING COMPANY, OF NEW YORK, N. Y., A CORPORATIONOF NEW JERSEY PURIFICATION or CERAMIC MATERIALS LBY SODIUM OYANIDE No Drawing.

ticularly to the removal of impurities which 5 introduce into'the finished product various objectionable shades of color.

The invention is particularly applicable to the purification of materials used in the manufacture of enamels, as for example, white enamels in which traces of color are particularly objectionable.

The invention further consists in the new and novel features of operation and the new and original'arrangements and combinations of steps in the process hereinafter described and more particularly set forth in the claims.

Although the novel features which are believed tobe characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the modeof its operation and the mannner of'its organiza tion may be better understood by referring to the following description in which a particular commercial embodiment thereof is disclosed. It will be understood, however, that the processes and the steps thereof may be modified in various respects without departing from the broad spirit and scope of the invention.

In the following description and in the claims the various steps in the process and the details comprising the invention will be identified by specific names for convenience but they are intended to be as generic in their application as the art will permit.

The present process utilizes the fact that certain metals form cyanides or double cyanides which are soluble in water. Examples of such metals are lead, mercury, arsenic, tin, bismuth, cadmium, copper, aluminum, iron, cobalt, nickel, zinc, manganese, silver and gold. Also many of the oxides of the metals are soluble in certain cyanides, such as sodium cyanides, and certain insoluble salts of the metals become soluble as complex cyanides. V

Certain metals, oxides and salts, when present even to the extent of several percent, have no coloring effect on the finished prod- Application filed December 26, 1930. Serial No. 505,000.

purity having no effect when present alone is colloidally dispersed in a second impurity which also when present alone would be harmless, and pronounced shades result from the dispersion. Hence, it may be possible to remove one impurity whichfunctions as a dispersing agent for another impurity and thereby prevent the second impurity from remalnlng in the condition of acolloidal dispersion whereby it will have no detrimental effect on the finished product even though it hasnot been removed therefrom.

The present invention will be particularly described as applied to the removal of various impurities from sodium antimonate which is used as an opacifying agent'in white enamels. This material may be obtained from metallic antimony and sodium'hydroxide or may be obtained as a-b'y-productin lead softening or in other well known manners and contains various impurities which U the finished white enamel.

These lmpuritles are removed 1n accordintroduce .objectionableshades of color into 'ance with the present invention by leaching the antimonate withal cyanide solution, such as sodium cyanide, which is capable of dissolving the undesired metals or rendering them harmless in the manner outlined above.

In carrying out this process sodium cyanide, either as a water solution or in the v, solid form, may be added to a mixture comprising approximately equal parts of weight of sodium antimonate and water. The mixture is then stirred for a sufficient length of time to permit the leaching action to be completed, as for example, three hours, after which the product is allowed to settle and may be decanted or filtered. The decanted liquid or filtrate may be found to be colored yellowish, the intensity of color depending upon the amount'of impurities originally a reasonable length of time in contact with the sodium antimonate as certaincomplex cyanldes tend to decompose and pass out of the solution again contaminating the product. It is preferable to decant or filter the cyanide solution as soon as the solid material is settled which may require from 12 to 24 hours.

As a specific example of the effectiveness of the present process a sample of sodium antimonate was used as an opacifying agent inthe preparation of a white glaze. The resulting glaze was discolored to a chocolate brown color. The sodium antimonate was .then washed with 4% of sodium cyanide and a cream color glaze resulted. Vhen the antimonate was again washed with an additional 2% of sodium cyanide it produced a pure white glaze. V V As a further example, a sample of sodium antimonate produced an enamel so nearly white that the difference was only noticeable with a close comparison with a standard, but was sufiicientlygreat to render the same unsuitable for themarket. The sodium antimonate was then treated with .8% of so dium cyanide after which it produced a pure white enamel equal to the standard.

Although the above process has been particularly described as applied tothe purification of sodium antimonate it is to be'understood that it is equally applicable to calcium stannate other ceramic materials containing impurities which are soluble in cyanide solutions. It is also obvious that potassium cyanide or other water'soluble cyanide may be used as the leaching agent.

Although certain novel features of the in Vention have been shown and described and are pointed out in the annexedclaims, it will be understood that variousomissions, substitutions and changes in the several steps of the process and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is: 1 1. The process of purifying opacifying agents used in enamels, glazes and glasses to remove impurities therefrom which are capable of introducing an undesirable color into the finished product which comprises'treating said opacifying agents with-a-cyanide solution whereby the undesirable materials are dissolved andseparated therefrom, and :then

separating removing the opacifying agents from the solution.

2. The process of treating opacifying agents used in enamels, glazes and glasses for the removal of impurities therefrom which would be capable of introducing undesirable colors into the finished product which comprises forming a mixture of said opacifying agent and water and adding thereto a cyanide and causing an intimate mixture between the cyanide and said opacifying agent whereby impurities are dissolved therefrom and then separating the ceramic material and the cyanide solution.

3. The'proc'ess of" purifying sodium antimonate to remove impurities therefrom which would be harmful in the production .ofenamels, glazes and glasses which comprises treating said sodium antimonate with a cyanidesol-ution for a sufficient period. of time to extract the undesiredfimpurities, and the antimonate fromsaid solu tion. 1'. v

4. The process of purifying sodium antimonate to'jremove impurities'therefrom whi ch 7 would be harmful in the "production of enamels, glazes and glasses which comprlses leachmg said sod um antimonate 1n a cyanide solution for a suflicient periodof time to extract the undesired" impurities, and separating the antimonate from said solution.

'5.-Theprocess of purifying sodium antim'onate'to remove impuritiestherefrom which would be harmful in the production of enamels, glazes and glasses which comprises leaching said sodium antimonate in a sodium cyanide solution for a sufficient period of timeto extract the undesired impurities, and separating the antimonate from said so1ution. r

6. The process of purifying sodium anti- 'monate for use in ceramics which comprises -add1ng sodium cyanlde to a mixture of sodlum antlmonate and water, stirring to effect an intimate contact, allowing the antimonate to settle and decantmg the cyanide solution. 7. The process of purlfying sodium antimonate to render the same suitable for ceramics which comprises leaching said antiof a sufficient amount of alkali to retard the hydrolysisof the cyanide.

8. The process of purifying sodium anti- -monate which comprises leaching the same with sodiumcyanide in the presence of an amount of sodium hydroxide sufiicient'to impart an alkalinity to the solution and to retard the hydrolysis of the cyanide.

9. The process of purifying an opacifying agent used in enamels, glazesand glasses to remove undesirable impurities which oomprises leaching said opacifying agentin an alkaline cyanide solution. i

.10. T he process of purifying an opacifying agent used in enamels, glazes and glasses to 'monat'e with sodium cyanide in the presence remove undesirable impurities which comprises leaching said opacifying agent in an alkaline solution of sodium cyanide.

11. The process of purifying an opacifying agent used in enamels, glazes and glasses to remove undesirable impurities which comprises leaching said opacifying agent in a solution of sodium cyanide.

12. The process of purifying an opacifying agent used in enamels, glazes and glasses to remove undesirable impurities which comprises leaching said opacifying agent in a cyanide solution.

In testimony whereof I have hereunto set my hand.

EDGAR A. SLAGLE. 

